The present invention refers to a lintel for supporting the first course at the walling of e.g. arches over wall openings, brick facades and similar, said lintel having a substantially L-shaped cross section.
When arches over wall openings, as windows and door openings, are walled usually prefabricated prestressed courses of brick are used, which form both the centering and the first course at the walling. Prestressed facade courses are manufactured by solid brick and usually comprise bricks provided with grooves and a prestressed reinforcement are casted into said grooves. In some cases also arches walled in situ are used, at which a wood girder supported by posts, which are removed after the walling, is placed in the wall opening. A third alternative is that an iron girder, e.g. a L- or I-beam is walled in and permanently supports the arch. This alternative is however used only in such cases, e.g. for industrial buildings, where no greater claims for an aesthetical exterior are called for. Also in these cases the separate stones consist of a solid stone material.
Since the facade stones in most cases are hollow blocks and these are manufactured in many different tints and surface structures it is necessary to provide also the solid stones in all these tints and structures, which requires large storage spaces. Besides that it is very difficult to achieve the same tint for a hollow brick as for a solid brick when burning the bricks. Thus it is desirable to be able to use hollow bricks also for the first course when walling an arch, but this has not been possible since the hollow side of the bricks would be visible.
Facade coverings of bricks are always built up at a distance from the house wall, so that a ventilator opening is formed between the wall and the facade covering. The claim for more hard-burnt bricks has also involved that their water absorption ability has been considerably reduced and this has resulted in a formation of fine contraction cracks between the bricks and the mortar joints, said cracks due to capillary effects transport considerable amounts of rainwater from the outside of the facade to the inside of the facade covering. This amount of water can be so big that the water runs along the backside of the facade bricks facing the house wall and serious damages can occur if a satisfactory drainage has not been arranged. Attempts have been made for arranging the drainage above window- and door frames by attaching sealing strips of board or similar, but it has hitherto been difficult to achieve a satisfactory drainage, since the window frame often is mounted at a later occasion and the drainage problem has then not sufficiently been taken into consideration or has even been forgotten.
In many cases it is now also desired that in connection with the facade covering an additional insulation should be applied, which makes the facade covering -- bricks -- to be situated 10 - 12 cm outside the wall. In such cases L-beams are required, where at least one of the shanks has a length of 130 - 200 mm, which however involves that the running meter costs for such galvanized standard beams will be unreasonably high, at the same time as the L-beam due to its high weight requires extra strong attachment means in the wall and thus means a complication.
Bearing beams are previously known in a plurality of different embodiments. The main part of them implies a fixed connection to the wall behind, which for lintels is a drawback, since the distance between the wall behind and the backside of the mortar in practice impossibly can be kept constant, i.a. due to that the wall never is completely straight and that the bricks have large size tolerances. This results in that the front edge of the lintel will follow the irregularities of the wall and thus be deformed and attain a more or less pronounced arch shape both in the vertical and horizontal direction. An important condition is therefore that lintels are so designed that they do not have to be connected to the wall behind, but at the same time have such a carrying capacity that they can carry the whole load from the arch plus the load loading the arch.
According to a known construction (the British Pat. No. 1.218.082) the lintel is designed as a plate profile and is intended to be walled up in a back brick wall, which is walled up at the same time. This implies that the joints in the front and the back wall are situated at exactly the same height, which practically never is the case. The lintel is further not designed for carrying the load from an arch above a window- or a door opening or the load from a whole facade brick wall, since a deflection of the horizontal shank when subjected to a load cannot be avoided.
It has also been proposed (the British Pat. No. 694.214) to strengthen the lintel by means of stiffeners welded between the shanks of the lintel at a mutual distance corresponding to the length of a brick plus the width of a joint, but since the brick can have a length tolerance of .+-. 1 cm it is necessary to make the distance between the bricks correspondingly longer. By that the brick course resting on the lintel will have a considerably larger joint width -- 5 cm instead of normally 2 cm -- which is not acceptable. Besides that the welding of the stiffeners means such a complication and increase in price of the lintel, that it from economical aspects would not be preferable compared to if the thickness of material of the lintel had been increased so much, that the lintel could carry the occuring loads without stiffeners. An additional drawback with the lintels according to the British Pat. No. 694.214 is that it cannot be piled and thus neither can be put overlapping each other, e.g. in such cases where only very short store spaces are available. Another important drawback with welded stiffeners is that only one type of bonding can be laid, at which the freedom of choice is considerably limited. Providing lintels for every kind of bonding is unrealistic even if the above mentioned drawbacks are disregarded.